1. Field of the Invention
The present invention relates to a processing system, and more particularly, to optimizing processor operation in a processing system including one or more digital filters.
2. Statement of the Problem
Vibratory flowmeters typically include a processing system that operates a driver to vibrate a flowtube assembly, receives pick-off sensor signals in response, processes the pick-off sensor response signals, and communicates with external devices. The processing system processes the pick-off sensor response signals in order to generate one or more measurements, such as one or more flow characteristics. The one or more flow characteristics can include a vibration frequency, a phase difference or time difference between leading and lagging portions of a flow tube or tubes, mass flow rate, density, viscosity, pressure, and others.
The processing system can receive and digitize analog inputs. The digitizing may require sampling of the analog signal(s). The processing system runs at a fixed clock rate and samples the pick-off sensor response signals at a fixed sampling rate. According to the Nyquist Theorem, the sampling rate must be at least twice the frequency being sampled.
One processing system application is a flowmeter, such as a vibratory flowmeter, where the processing system receives analog vibrational signals and determines frequency and phase characteristics of the vibrational signals, among other things. In the past, the sampling rate has been set at a high enough frequency to accommodate various models of flowmeters, including low frequency flow meters and high frequency flow meters. This can be done for economic reasons, such as to avoid the manufacturing and tracking of multiple models of flowmeter electronics. Typically, the sampling rate has been set at 2,000 Hertz (i.e., 2 kHz), where most vibratory flowmeters operate at frequencies well below 1 kHz.
In the prior art, processing system speed is generally not a concern. The prior art processing system is typically chosen for durability and capacity. If the processing system has a high enough clock speed, the processing system will be able to adequately process the 2 kHz samples in order to generate the one or more flow characteristics (and may be able to perform additional processing and communications and control functions). Clock speed and sampling rate of the flowmeter electronics are generally configured for wide applicability and therefore have been chosen to significantly exceed flowmeter vibration rates. Processing system power consumption has not been a concern in the prior art and therefore it has been acceptable practice to set a generous sampling rate.
The drawback in using a high sampling rate is that it requires a high processing system clock rate. The high clock rate in turn forces a higher power consumption.
In some applications, it is desired to keep power consumption as low as possible. Consequently, high power consumption by the processing system is problematic.